In order to increase the atmosphere of swimming pool, there are manufacturers who provide lamps that float on the surface of water. However, the lamps are different from the life-saving lamp and sea-floating prompt light disclosed in the U.S. Pat. No. 9,347,629 and U.S. Patent Publication No. 2014/162509. Moreover, most of the lamps used in swimming pools today only focus on the lighting effect, and the design for floating stability is not taken into consideration, resulting in the lamps to be easily overturned by waves caused by swimmers.